Genetic engineering of chloroplast genome using a large-chloroplast mutant in rice

自20世纪80年代以来，人们一直在尝试高等植物叶绿体基因组的基因工程，并在烟草等多种植物中获得了成功。叶绿体转化具有优于核基因组的优点，因为i）基因组的母系遗传消除了转基因通过花粉的传播，ii）没有基因沉默允许转基因以高水平表达，以及iii）同源重组将转基因靶向到期望的基因组区域中。尽管有这些优点，但水稻和其他作物的叶绿体转化效率极低。我们推断，其中一个障碍可能是这些物种中叶绿体的尺寸较小。在这项研究中，我们建议利用一个突变体，扩大了叶绿体。分离和鉴定了一个显示大叶绿体的水稻突变体，鉴定了导致这种突变的基因，并尝试使用该品系进行水稻叶绿体转化。

Genetic engineering of chloroplast genome in higher plants has been attempted since 1980’s, and has been successful in tobacco and several species. Chloroplast transformation has advantages over nucleargenome, because i) maternal inheritance of the genome eliminates dispersal of a transgene through pollen, ii) no gene silencing allows transgene to be expressed at highlevel, and iii) homologous recombination targets a transgene into a desired genomic region. Despite such advantages, efficiency of chloroplast transformation is extremely low in rice and other crops. We reasoned that one obstacle may be a small size of chloroplasts in these species. In this study, we propose to utilize a mutant that has enlarged chloroplasts. Isolation and characterization of a rice mutant showing large chloroplasts, identification of the gene responsible for this mutation, and an attempt to use this line for rice chloroplast transformation, have been conducted.